Hey everyone-

So I'm coming off a long process of rebuilding the engine on my 03 R53. I got the car running last weekend and it seemed okay. Monday it started running rough and threw a cylinder 4 misfire code and o2 bank 1 sensor out of range. This morning it started up and quickly started dropping cylinders and eventually wouldn't run or start.

I ran a lot of diagnostics, the important one being a noid light. I managed to get one on in time to catch the last of a fading injector firing signal. Now I'm not getting anything on all 4 cylinders. The injectors are getting good power and continuity to the ECU checks out fine. I pulled open the ECU and nothing appears amiss.

My questions are:

Can this be anything besides a failed ECU?

If it is a bad ECU, is there any risk I have something hooked up incorrectly that will toast a replacement ECU?

Could this possibly be remedied with a re-flash?

Any other input is welcome too.

 

I just noticed that the ground/ECU signaling wires for the injectors are all making 3.5 volts when run to the block. Does that even make sense for ground triggered wires to be supplying voltage?

 

I have been trying to trace the wiring through the ECU. If I let the car sit a while it will run (poorly) for a few minutes before it cuts out again.

Could anyone tell me where the fuel injector's ground wire(s) are on the ECU? Having a pin-out diagram or even knowing where the wires route to a ground point would be helpful.

 

 

A little late on the reply, I know, but I'll answer in case anyone else has the same problem. I must have made a mistake during the rebuild and missed torquing the cam caps down because when I pulled the valve cover I found that most of the bolts had backed out. Because both the cam and rockers were loose the valves weren't actuating properly so my guess is that the ECU was confused and gave up. It may have also been that the camshaft position sensor wasn't getting a good signal too.

Lesson learned, don't stay up really late thrashing trying to finish something. Take your time, double check your steps.

I still have no idea why the fuel injector's wiring was behaving like it was, but when I tightened and torqued everything properly everything was fine.